Electric heater for windscreens and windows



Jan. 31, 1950 c. R. HOPKINS ELECTRIC HEATER FOR WINDSCREENS AND WINDOWSFiled Sept. 18, 1946 AND'WIND'OWS Cecil .BmbertHopkins, Glasgow,Scotland-- 1 Application S ptember 18, 1946, Serial memo um; .1 nmzl I,"J Y 5. T This invention relates to electric he ters "for inassocia-tidn'with windscreens and windows, especially the windscreens ofmotor road vehicles "although also windscreens and windows in gen-"eral, 'ror ereveri rig the formation of mist, frost "or ice 'on'thesurfaces of the windscreens or windows 5r for the'remova'l of mist,frost or ice from such'surfaces. "Hereinafter and in the appended "clairr'iwindscreens and windows are called windsc eens.

More particularly, the invention relates to electric heaters asaforesaid "of th'etype comprising a casing and an electric heatingelement extending withinthe'casing fromend to end thereof, the .casing'having a passage through which radiant heat is directed upwards from thecasing along theserfaee of the windscreen to be warmed. The air heatedin this way. rising over the suface, draws with it cool'airfr'ombe'lows'o that a stream .of warm air will pass upwards between thecasing and the surface and will safeguard the windscreen against damagefrom local overheating "such as might be caused by'hot'air'and raysdirected with excessive intensity upon the surface ,pr'oximitytothecasing. Electric heaters of V t the typestated do not require the useof'therin'ostatic-or other control means-to reduce-or cut-01f ,the'supplyof current to the elementand they .obviate ;all.need for subpanels or other obstructive intermediaries that are provided in otherheaters not of the'type stated to absorb the heat radiated by the heaterand spread it over the "surfacetobe warmed'.""""" Heaters of the typestated are supplied with current at low voltage. For instance, in thecase of motor road vehicles the voltage as a rule does not exceed 12volts, the current in each case being drawn from the battery circuit ofthe vehicle.

An object of the invention is to provide a heater of the type statedthat extends over the width of the windscreen and has a low-voltageelement of the requisite length and heating efliciency.

Another object is to provide a heater of the type stated having aheating element that consists of a ribbon-like resistance close-coiledso that the adjacent convolutions come sufiiciently close to one anotherto radiate effectively on one another and thus maintain a heating zoneof sufliciently concentrated intensity to set up the required flow ofheated air.

Another object, in order that the heater may be suitable for windscreensof different widths, is to provide a casing that is of telescopicconstruction so that it is extensible to difierent sizes 1 Claim. (Cl.219-19) a ainst the tension time coiled "having goodl'ic'at-"cohdubtingualities.

2( I TC. I I ribbon-like heating/element. I I 1 The invention'willr'iowbe more particularlyd scribed with reference to the accompanying sheetof drawings in'whichi i Fig. '1 isairo'nt elevationer-aheateroftelescopic construction. Fig. 2 is'an end'elevation 6f theheater in the direction of arrow 11 of'FigL-"l. Fig. 3- is a section toa larger scale o'nthe line I II --III o'frFi g. 1. Fig. eis a s'ectiononthe" line IV-IV of Fig. l'toth'e slaine'scale as Fig: 3. Fig. 5' isalarge 'scaleview of the close-coiled ribbonlike heating element. g i

i wet 'anbth'er form f'of telescopic casin I H er scale on the nae viiivl er Fig? 7 6. xIEig. '8 is a fragmentary front elevation showijng'attachment means fo'rinoiintin'g the heater on fram -k"as'sociated withtnewmdsereen; i

' 'a fragmentary; rear elevation corre} ticularlyto Figs. 1 to 5, inthis the "c'orisi'sits'of an intermediate about *feet 'long and terminalouter glitl larger diameter. the arrangehthatby sliding the tubesztelescopically along the" tube I against the" tension 'of-the"" iledribbon-like heating element 'ae'riiss' which the 'heater is efiecti'veihdscr'eenso-f-difiereiit ade of a metal or alloy Inor- -der"tol ensur'that *the tubes cannot come apart the tube is provided a-t it's' "endswith lug-s I which engage with inwardly projecting lips 5 on therelative ends of the tubes 2. The tubes I and 2 are each formed with along narrow slot, about 4 inch in width, and these slots form acontinuous open passage which extends practically throughout the lengthof the casing (see Fig. 1). Radiant heat is directed upwards through thepassage on to the surface to be heated at an inclined angle as indicatedby the arrow A in Fig. 3.

The heating element 3 consists of a long ribbon-like coil of appropriateresistant alloy, the coil material being oblong in cross-section. Thecoil is supported at intervals throughout its length by thick washers 6which fit neatly into the casing and which are composed ofelectricityinsulating refractory material.

In the example according to Figs. 1 to 5, at each end of the casingthere is attached a suction cup 1, each cup being provided with anattachment screw 8, connected to a lug 9 which is a terminal extensionof the associated tube 2. A nut Ill sites. tubes are made ofheat-insulating material serves to secure the screw and lug together. Awasher ll of similar material is interposed between the lug and thesuction cup.

In the foregoing example the heater may be to a part l6 of the dashboardof the vehicle by nuts ll, l8.

Fig. 9 shows the terminal 3A at one end of the heating element 3, saidterminal being a screw electricity-insulated by a ferrule 33 from thetube 2.

An alternative form of telescopic casing is shown in Figs. 6 and 7. Onthe inside of each end of the inner tube I there is provided a brassclip IS which is permanently attached to the tube i by riveting or othermeans. Each clip projects beyond each side of the slot in the tube l andis .bent over to form lips 20 which engage over the rims of the tubes 2so that the tubes may readily slide along one another, thus providingfor adjustment of the length, or widthwise span, of the whole casing.Midway between the ends of the tube l is a ring 2| which fits neatlyover the tube and acts as a buffer for the tubes 2 in the telescopicallycontracted position'of the casing.

As Fig. shows, the ribbon-like resistance 3 is closely coiled. Thedesign is such that adjacent convolutions come close to one another inorder to radiate effectively on one another and thus provide a source ofconcentrated heat. Heat rays from this source (arrow A, Fig. 3)radiating through the long narrow passage in the casing heat the air ina zone extending along the exterior of the passage. This heated airrises and, in rising, induces cool air to flow upwards between thecasing and the windscreen or window. Thus, a stream of warm air flowsupwards over the surface of the windscreen or window.

Current for the heater is drawn from say an electric battery circuit byleads 22, and the heater may be switched on and off by a switch 23 ofany known type. In the example the switch is of a one-way type situatedat one end of the heater. as illustrated in Fig. 2; alternatively, atwo-way switch may be used, and the switch may be located at anyconvenient point in the leads.

The heater may be modified in various respects without departing fromthe invention. For example, although it is preferable that the casingshall be part-cylindrical (because the cylindrical form facilitatesmanufacture and is effective in heat conservation) it may be of othersectional form. For instance, the casing may be angular or polygonal incross-section, in which event the interior ofthe casing presents fiatreflecting surfaces behind the element, instead of a circular reflectingsurface as in the example. The casing need not be made of a metal oralloy; it could be made for instance of appropriate thermosettingplastic material in which event there may be no need to make provisionfor heat insulation or electricity insulation between the ends of thecasing and its mountings. The passage for heated air need not beconstituted as a single uninterrupted slot; there may be two or moreslots or a series of holes spaced apart.

I claim:

A heater of the type stated comprising a casing consisting of aplurality of parts in telescopic relationship,,which parts areextensible to vary the effective heating length of the casing, meanslimiting the extent of extensibility of saidparts, a slot in each ofsaid parts providing a continuous open passage extending lengthwise ofthe casing, and a heating element arranged in said casing alongside saidpassage and consisting of a ribbon-like resistance close-coiled so thatthe adjacent convolutions come sufficiently close to one another toradiate effectively on one another and thus provide a source ofconcentrated heat which acts through said passage to maintain a heatingzone along the exterior thereof.

CECIL ROBERT HOPKINS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,744,100 Bouchard Jan. 21, 19301,754,669 Cohen Apr. 15, 1930 1,835,602 Kercher et al. Dec. 8, 19311,852,599 Zaiger et al Apr. 5, 1932 1,942,359 Horton et al. Jan. 2, 1934FOREIGN PATENTS Number Country Date 1 501,683 Great Britain Mar. 3, 1939

